Patent Literature 1 describes a technique in which, in a power supply apparatus of a gas-laser oscillator, an alternating-current voltage of a commercial power supply is converted into a direct-current voltage in a converter unit and input to an inverter unit, the direct-current voltage is converted into a square-wave alternating-current voltage in the inverter unit including a switching device and a free wheeling diode, and an output voltage of the inverter unit is boosted by a high-frequency transformer with inductance and applied between dielectric electrodes, so that a discharge occurs between the dielectric electrodes. In this power supply apparatus, a reactor is connected in parallel to the high-frequency transformer on an output side of the inverter unit. Therefore, according to Patent Literature 1, because a recovery current flowing in the free wheeling diode in the inverter unit can be reduced when any discharge does not occur between the dielectric electrodes, it is supposed that heat generation of the free wheeling diode can be suppressed.
Patent Literature 2 describes a technique in which, in a laser power supply apparatus, a rectifying unit rectifies a commercial alternating-current power supply, the rectified voltage is smoothened into a direct-current voltage and boosted by a step-up converter unit, the boosted direct-current voltage is converted into a high-frequency voltage by an inverter unit, and the high-frequency voltage is boosted to a voltage to be applied to a discharge electrode unit for laser excitation by a step-up transformer. Therefore, according to Patent Literature 2, because a turns ratio (a boost ratio) of the step-up transformer can be reduced by boosting the commercial alternating-current power supply by the step-up converter unit, it is supposed that a secondary-side leakage inductance that is proportional to a square of a secondary-side number-of-turns can be reduced.
Patent Literature 3 describes a technique in which, in a direct-current power supply apparatus, a rectifier rectifies an alternating-current input power supply into a direct-current voltage and inputs the direct-current voltage to an inverter, the inverter converts the direct-current voltage into a high-frequency voltage, and the high-frequency voltage is applied to primary windings of two isolation transformers connected in parallel to each other and to two windings of a coupling transformer. According to this direct-current power supply apparatus, the two windings of the coupling transformer magnetically couple an input current path of one polarity of the primary winding of one of the two isolation transformers to an input current path of the other polarity of the primary winding of another isolation transformer at a turns ratio of one. Therefore, according to Patent Literature 3, equal currents flow in the two windings of the coupling transformer in a forcible manner and equal currents flow in the respective primary windings of the two isolation transformers in a forcible manner, and thus it is supposed that the currents of the isolation transformers are balanced.